Kinetics of Microbial Reduction of Solid Phase U(VI)

Authors

Chongxuan Liu, Pacific Northwest National LaboratoryFollow
Byong-Hun Jeon, Yonsei University
John M. Zachara, Pacific Northwest National LaboratoryFollow
Zheming Wang, Pacific Northwest National LaboratoryFollow
Alice Dohnalkova, Pacific Northwest National Laboratory
James K. Fredrickson, Pacific Northwest National LaboratoryFollow

Date of this Version

2006

Citation

Environ. Sci. Technol. 2006, 40, 6290-6296

Abstract

Sodium boltwoodite (NaUO₂SiO₃OH•1.5 H₂O) was used to assess the kinetics of microbial reduction of solid-phase U(VI) by a dissimilatory metal-reducing bacterium (DMRB), Shewanella oneidensis strain MR-1. The bioreduction kinetics was studied with Na-boltwoodite in suspension or within alginate beads in a nongrowth medium with lactate as electron donor at pH 6.8 buffered with PIPES. Concentrations of U(VI)_tot and cell number were varied to evaluate the coupling of U(VI) dissolution, diffusion, and microbial activity. Microscopic and spectroscopic analyses with transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and laser-induced fluorescence spectroscopy (LIFS) collectively indicated that solid-phase U(VI) was first dissolved and diffused out of grain interiors before it was reduced on bacterial surfaces and/or within the periplasm. The kinetics of solidphase U(VI) bioreduction was well described by a coupled model of bicarbonate-promoted dissolution of Naboltwoodite, intragrain uranyl diffusion, and Monod type bioreduction kinetics with respect to dissolved U(VI) concentration. The results demonstrated that microbial reduction of solid-phase U(VI) is controlled by coupled biological, chemical, and physical processes.